Field of the Invention
This specification relates to a wireless communication, and more particularly, to a method and apparatus for transmitting a sound reference signal by a terminal.
Related Art
The third generation after the next generation mobile communication system IMT (International Mobile Telecommunication)-Advanced standardization work in the ITU-R (International Telecommunication Union Radio communication sector). The support of multimedia services in IP (Internet Protocol)-based IMT-Advanced stop and slow the progress of the move from 1 Gbps to 100 Mbps data transfer rate from the fast-moving state and goal.
The 3GPP (3rd Generation Partnership Project) transmission scheme based on OFDMA (Orthogonal Frequency Division Multiple Access)/SC-FDMA (Single Carrier-Frequency Division Multiple Access) system to meet the requirements of IMT-Advanced standard LTE (Long Term Evolution improved LTE-Advanced) is being prepared. LTE-Advanced is one of the prime candidates for IMT-Advanced.
Some examples which may be applied to a next-generation communication technology such as LTE-A are carrier aggregation (CA) and cooperated multi-point transmission. The CA is a technology that provides a broadband by aggregating a plurality of carriers including a narrow band. The cooperated transmission is a technology that improves and system performance and efficiency by transmitting signals to the same receiving terminal by cooperation of a plurality of transmitting terminals.
Further, the terminal transmits reference signals to measure the uplink channel state. A reference signal, which is not related with uplink data or uplink control information which is transmitted by the terminal among such reference signals, is called a sounding reference signal (SRS). The sounding reference signal may 1) be periodically transmitted or 2) receive a triggering signal, and then be aperiodically transmitted.
According to a conventional art, it has been stipulated that a carrier which is used when aperiodically transmitting a sounding reference signal is an uplink carrier linked by a downlink carrier via which a data channel has been received, and system information. However, when carriers are aggregated, the terminal may receive a data channel via the downlink carrier without the linked uplink carrier. Furthermore, at the cooperative transmission, even if a data channel is received through the downlink carrier with the linked uplink carrier, the uplink transmission through the linked uplink carrier may not be set at the time point when the sounding reference signal is transmitted.
Hence, there is a need for a method and apparatus for transmitting a sounding reference signal of a terminal which may be performed in the above case.